The invention relates to an air filter casing of an internal combustion engine which includes an air filter element dividing the interior of the casing into an unfiltered air chamber for receiving the uncleaned combustion air and a clean air chamber for receiving the cleaned combustion air.
With an air filter casing of this type, which is known from German Utility Model No. 19 81 035, there is provided at its clean air end, in the area of an angled intake tube which recycles the venting gases of the crankcase, a recess in the casing bottom with the aid of which recess the condensation water which may be entrained with the crankcase venting gases can be prevented from being aspirated by the internal combustion engine. However, with an unfavorable arrangement of the suction pipe on the unfiltered air side it must be expected during operation in relatively heavy rainfall that the water which is sucked in with the combustion air can settle after a certain time in the clean air portion of the air filter casing and collect there to such an extent that in the event of acceleration or deceleration a larger quantity of water can pass into the suction pipe and thus enter the combustion chamber of the internal combustion engine.
An air filter casing is also known from German published unexamined application (DOS) No. 31 30 782, at the bottom of which casing there is provided on the unfiltered air side a relatively costly valve for draining water from the air filter casing.
In the case of an air filter casing shown in German published unexamined application (DOS) No. 34 29 633, a controlled multiple deflection of the aspirated combustion air and consequently suppression of the intake noise are achieved by partitions attached to the upper part of the casing and to the casing bottom. However, this multiple deflection of the intake air has an adverse effect on the volumetric efficiency of the internal combustion engine.
A problem underlying the invention is therefore to create an air filter casing of the general type described above in which any water collected on the clean air side of the air filter casing can be kept to a minimum during operation in heavy rainfall without any appreciable adverse effect on volumetric efficiency.
This problem is solved in accordance with the invention by providing a device in the clean air chamber which starts from the upper part of the casing and ends in the area near to the bottom of the casing, for swirling water which settles at the bottom of the casing.
The device according to the invention which is arranged in the clean air chamber of the air filter casing ensures that even in the event of very small accumulations of water, the water swirls to such an extent because of the strong flow of intake air that negligibly small quantities of water are also aspirated continuously by the internal combustion engine and discharged again in the form of water vapor during the engine exhaust cycle.
Consequently, the water level established in the stationary state in the clean air chamber remains so low that aspiration of larger quantities of water which are critical in terms of damage to the internal combustion engine is excluded.
In especially preferred embodiments the water swirling device is constructed as a partition wall connected to the top and side walls of the casing and extending downward to a small spacing from the bottom casing wall. Certain preferred embodiments have the partition wall spaced by about 35 mm from the casing bottom wall and the bottom of the partition wall is rounded.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.